First I will look at the project itself, then
1.read whitepaper
2. check the team (good project should have strong team!)
3. check rating websites
How many ICOs do you invest in then?
To be honest I do not remember precise number, but it should be little bit over 10. It was before better to invest during ICO. Nowadays, when ICO ends and token are available in exchange sites, the price become usually lower than ICO. I believe this is because of boundy hunters whose numbers have increased a lot in the past year. Boundy hunters usually dump their coins at low price.